Zidovudine (ZDV), Didanosine (ddI), Stavudine (d4T), and Lamivudine (3TC), are commonly used as single agents as well as in combination for treatment of HIV infection in children. Accumulating information suggests that combination therapy with two or more antiretroviral agents, however, may hold more promise than single-agent therapy in the long-term management of HIV infection. In addition, as resistance to common medications occurs, it becomes increasingly important to investigate new medications that may be used to treat HI-infected infants and children. A high priority for children infected with HIV is the development of an effective, safe, and tolerable protease inhibitor to add to the arsenal against the virus. The short-term safety profile of 141W94 indicates that it is well tolerated by adults and results in significant decrease in plasma HIV RNA concentration, and increases in CD4+ lymphocyte counts. PROAB3004 is a randomized double-blind, placebo-controlled phase III study of nucleoside therapy with versus without the addition of 141W94. Throughout the United States, 210 children 6 months through 18 years will participate, starting with the older age cohort, and, as the pediatric doses are developed, extending to all age groups.